The present invention relates to apparatus for the distribution evaluation of regional lung ventilation by means of the absorption of radioactive radiation emitted by an enclosed radionuclide which after passing through the subject being measured, is sensed by a set of scintillation detectors.
At present, the nonuniform distribution of regional lung ventilation is most frequently judged from the prolonged mixing time, when breathing gaseous mixtures, while tracing the change in the concentration of a selected gas. In this case, the so-called wash-out or wash-in method can be employed. During tracing either nitrogen, inert gases, or radiopharmacons can be used. The methods employing the direct concentration measurement of nitrogen or inert gases, however, have a common disadvantage which consists in the fact that these methods are not sufficiently precise and therefore, can be used only for a general orientation. The location of the disorder is, however, impossible if these examinations are not carried out by gas sampling by means of gas analyzers corresponding to the gas used for the given purpose, the samples of the alveolar gas being taken from the bronchial tree. Another disadvantage of the examination of the regional function resides in the fact that the detected radiation of an isotope applied on the patient's body is also strongly influenced by the radiation absorption in the chest-wall and in the pleural effusion and so on, the magnitude of which cannot be designated, whereby the absolute and the relative evaluation of the regional ventilation is changed by a substantial fault making the result inaccurate.
The introduction of catheters is, however, unphysiological and pretentious for both the examining doctor and the patient. The application of radiopharmacons permits the localization of the changes to be determined, e.g. by means of a gamma camera. However, economically it is very pretentious and owing to the use of open radionuclides, it is possible only in special medical situations. The application of open radionuclides is also disadvantageous environmentally, and of the radiation loading of both the patient being examined and the examining physician. A certain contribution to remedying these insufficiencies of the methods mentioned above could be obtained from the application of the modified apparatus as described in the Czechoslovak Patent Specification, No. 196 123 (Simecek-Ryba: "The Apparatus for the Examinations of the Regional Lung Function"). By that apparatus regional ventilation can be registered but without the possibility of comparing and more exactly evaluating the changed distribution. The deficiency in that apparatus, however, can be seen in the fact that the number of the lung fields to be observed simultaneously is limited due to the low number of the available tracks of the lung fields to be observed simultaneously is limited due to the low number of the available tracks of the used recorder so that, in this case, the operations should be repeated during routine examinations. Owing to that, the accuracy of the evaluation has been considerably decreased with respect to the nonreproducibility of the conditions of the individual examinations following one another while simultaneously both the medical division and the patient being examined are exceedingly exposed to stress.